Surface Activity Monitor

DOE-HDBK-1129-99

5.9.2.b Surface Activity Monitor

A new surface activity monitor (SAM) for measuring tritium on metal (electrically conducting) and

non-metal (electrically non-conducting) surfaces has been recently developed at Ontario Hydro

Technologies. [30-32]

The monitor detects tritium on the surface and in the near-surface regions by virtue of primary

ionization in air due to the outward electron flux from the contaminated surface. The resulting ion

pairs are measured by imposing an electric field between the contaminated surface and a collector

plate. A simple theoretical model relates the total tritium concentration on a surface to the

measured current.

Experiments benchmarking the application of the surface activity monitor on metal surfaces

against independent measurement techniques of aqueous dissolution and thermal desorption

show equivalence in the total tritium activities measured. Comparison of surface activity monitor

measurements with the dry polystyrene smear protocol has shown that the two methods are

complementary. Smearing measures the activity removed by the smear action, which can be used

to infer the total activity on the surface. Surface activity monitor measurements determine the total

activity on the surface, which can be used to infer removable activity. Ontario Hydro has stated

that this device is the only surface monitor for tritium that provides an absolute measurement of the

total activity on metallic surfaces.

Experiments demonstrating the application of the surface activity monitor on a variety of non-

conducting surfaces have been conducted. Some of the non-conducting surfaces examined

include paper, concrete, granite, and wood. Experiments are underway to extend the database of

non-conducting materials measured by SAM and catalogue the associated collection efficiencies.

Currently, the SAM is commercially available in two models, QP100 and QP200, which have

measurement ranges of 0 - 200 nCi/cm2 and 0 - 200 Ci/cm2, respectively. A summary of the

technical specifications of the instrument is given in Table 5-2.

5.9.3.c Breathalyzer

A device undergoing development in Canada is the Scintrex Tritium-In-Breath Monitor. It is an

automatic monitor dedicated towards health physics and radiation biology applications. The

Tritium-in-Breath Monitor measures levels of exhaled tritium within 5 minutes of sampling, thus

saving considerable time and effort in the monitoring process. This rapid assessment has a

sensitivity level of 5Ci/L-urine equivalent, which may be sufficient for alarming the cautionary

levels of in-body tritium. Preliminary development of this equipment has been done at the Atomic

Energy of Canada Ltd. research laboratory in Chalk River, Canada.